Mayor Michael Bloomberg said Thursday his administration fulfilled a promise to plow every city street, but elected officials and others insisted some streets never saw a plow before the 7 a.m. deadline, marking another setback for the beleaguered mayor.

Mr. Bloomberg, who on Friday completes the first year of his third four-year term as the chief executive of the nation's largest city, has been besieged by a number of embarrassing episodes in recent weeks, with some saying he's endangering his image as an expert manager.

Council Member Debi Rose of Staten Island, who met with the mayor during his tour Thursday of every borough outside Manhattan, said she believes the city's sluggish response to the post-Christmas blizzard has dealt a serious blow to the mayor's reputation.

"This could be the straw that breaks New York City's back in terms of how well they think, a good job, the mayor has done," said Ms. Rose.

"I was stranded for three days myself. I could not get out," Ms. Rose said. "Something went drastically wrong with this snow removal."

The mayor said the administration plans to conduct a full investigation into the city's response to the storm. That probe will include examining allegations that disgruntled members of the Department of Sanitation deliberately slowed the snow removal as a protest.

The mayor and Sanitation Commissioner John Doherty on Thursday said they don't believe there was a coordinated slowdown.

"I don't think it took place but we're going to do an investigation to make sure that it didn't," Mr. Bloomberg said. "It would be an outrage if it took place. But I just don't know."

During a news conference in Queens, Mr. Bloomberg again conceded that his administration's response to the storm was both "inadequate and unacceptable," an about-face from his defiant stance during the early portion of the cleanup effort.

"Clearly the response to this storm has not met our standards or the standards that New Yorkers have come to expect from us," he said. "The long delays in plowing some of the city streets should not have happened. We're not making excuses."

At the same time, Mr. Bloomberg said the city met its commitment to plow every street, except those blocked by stranded vehicles, at least once by 7 a.m. Thursday.

The mayor estimated there were about a dozen of those blocked roads in one section of Brooklyn and a handful of others elsewhere.

Some city residents and elected officials disputed the mayor's contention.

"We still have quite a few blocks that have not been touched, still have quite a few blocks," Brooklyn Borough President Marty Markowitz said.

He added: "There is no excuse for this—absolutely no excuse. This was an outrage."

Moments after the mayor finished speaking, Queens Borough President Helen Marshall, who hadn't been invited to speak, approached the lectern to dispute the mayor's remarks.

"Most of the roads, even where I live, there's still about four inches right where the cars and everything go," she said. During the last several days, she said, residents from nearly every section of Queens called her office, saying, "Where is the plow? Where is the plow?"

For the mayor, the poor response to the snow storm comes on the heels of federal prosecutors arresting six people on charges of stealing $80 million allocated to the city's long-delayed computerized payroll system, known as CityTime.

The mayor's critics have lambasted Mr. Bloomberg for failing to police the CityTime project. In recent months, the mayor has also taken heat from some for the city's uptick in homicides, his plans to close fire companies, the secretive process for selecting the new schools chancellor and for failing to stand up enough for the working poor.

"It's been all malaise, no magic, thus far in the third term, with a record number of working poor New Yorkers now relying on food stamps and feeling invisible to and forgotten by this mayor," said Dan Morris, a spokesman for a coalition seeking a living wage law.

A mayoral spokesman, Stu Loeser, responded by saying: "We're proud that New York City led the nation for job creation over the last year, often creating jobs at twice the rate of the rest of the country."

Mr. Bloomberg said on Thursday he believes his campaign to seek a third term was the right decision for both him and the city.

"One of the reasons I wanted to run again was that we're going to be going through some very difficult times and it's never easy to go through difficult times," he said. "Bad times require a dedication and a commitment and a desire to make sure that this city comes through."

The mayor said he's more committed than ever to lead the city. While he accepted some responsibility for some of the administration's shortcomings, he said, "There's an awful lot of good numbers out there, as well."

Mr. Markowitz, who supported the mayor's bid for a third term, said "this is not the shining moment" for Mr. Bloomberg.

"But in anyone's life, you have ups and downs," Mr. Markowitz said. "He'll be up again."